The present invention relates to a mechanism suitable for ensuring alignment within a camera of film having pre-exposed latent images thereon, and to a camera incorporating such a mechanism, and to a film frame counter resetting mechanism.
It is known to provide photographic film which has been partly exposed in regions of each film frame with an image which is retained as a latent image. The user who loads the film then exposes the film in the normal manner in a specially adapted camera. The camera includes some masking arrangement to mask out the area of the film which bears the latent images, so that these are not double-exposed. When the film has been exposed by the user, it is processed and developed in the normal way, the finished pictures bearing both the pre-exposed images provided by the manufacturer (hereinafter referred to as xe2x80x9cpre-exposed imagesxe2x80x9d), and the user-exposed images thereon. For example, it can be arranged that the film is pre-exposed with a decorative strip which carries a message such as xe2x80x9chappy birthdayxe2x80x9d or xe2x80x9cwish you were herexe2x80x9d, the camera including a strip-like mask in the exposure window to prevent double-exposure of the pre-exposed film region.
It has been previously proposed by the applicant to provide such a film in a package or assembly comprising a standard 35 mm cassette and a second spoolless film container into which the film is wound extending from there to the cassette. Such a film package is disclosed for example in applicant""s U.S. patent application Ser. No. In use, the assembly is fitted into the camera with the cassette and film container arranged on opposite sides of a film exposure window. As pictures are successively taken the film is progressively wound out of the film container back in the cassette, finally being wound back fully into the cassette which can then be removed by the user for developing and processing. The film container is then discarded.
A particular problem arises in seeking to align the film in the camera, since it is necessary that the film be precisely positioned in the camera so that the pre-exposed images align precisely with the exposure window of the camera and hence the user-exposed images.
In one aspect the present invention is directed to ensuring this alignment.
In a first aspect the invention provides a camera for use with film bearing a series of latent pre-exposed images for subsequent user-exposure, comprising a film sprocket mechanism extending into a film passageway, the sprocket mechanism having a plurality of equidistantly-spaced teeth including an alignment tooth which is visually distinguishable from the other tooth, and comprising a main wheel part on which said other teeth are formed, and a separate part securable to the main wheel part which carries the alignment tooth.
The alignment tooth may be formed of a different colour to the other teeth, either by painting the alignment tooth or moulding it of a different coloured plastics material.
These parts may be formed of moulded plastics where the plastics are of contrasting colours. The main wheel part may define a part-annular recess, and the alignment tooth extends from a part-annular insert receivable in said recess. The sprocket wheel may be operatively commented to a shutter mechanism and wind-on mechanism where rotation of the sprocket wheel is arranged to effect re-cocking of the shutter mechanism. The wind-on mechanism prevents rotation of the sprocket wheel when the shuutter is re-cocked. In the re-cocked state of the shutter mechanism the alignment tooth extends rearwardly within the camera towards the film passageway.
In a further aspect the invention resides in a sprocket wheel as defined above.
In a further aspect the invention resides in a method of loading film bearing a series of pre exposed latent images for subsequent user-exposure into a camera having a film sprocket wheel operatively connected to a shutter mechanism and provided with a film alignment tooth, comprising the steps of: a) opening the camera back; b) rotating the film sprocket wheel until the film alignment tooth thereof extends towards the film passageway, and until the shutter mechanism is re-cocked; c) inserting film into the camera so that an alignment mark on the film is aligned with the alignment tooth; and d) closing the camera back.
A further problem with simple cameras of this type where the user reloads the film is in re-setting of the film frame counter, and a second aspect of the invention is directed to a mechanism for carrying out this resetting.
In a further aspect directed to resetting of the film frame counter, the invention resides in a camera having a pair of film-receiving chambers arranged on opposite sides of an exposure window between which, in use, film extends through a film passageway: a film sprocket wheel having a plurality of teeth which, in use, engage a film extending within the film passageway; a film counter drive wheel operatively connected to the film sprocket wheel driven by rotation of the sprocket wheel; a pivotably mounted film frame counter wheel mounted on a displaceable pivot engageable with the drive wheel; and resilient means which urge the film frame counter wheel to a reset position in which the film frame counter wheel adopts a predefined orientation.